CHEMISTRY COMMUNITY

eduardomorales5

How can we tell which compound is the catalyst based on the elementary reactions? How would we determine the reaction mechanism when we are not told which reaction is slow and which is fast?

eduardomorales5

What is the difference between an initial rate for a reactant, and its unique rate? Does this tie into the inverse of the stoichiometric coefficient?

eduardomorales5

How does an increase in temperature lower the activation energy? If we were given two reactions, 1 endothermic and the other exothermic, how would an increase in temperature affect the rate constant?

eduardomorales5

How would we find the change in entropy for an irreversible system? Why would the entropy of the surroundings equal 0?

eduardomorales5

The equilibrium constant, K, shows where the system reaches equilibrium, so that no work is being done by the system (Gibbs=0). Different value of Q will show how much work a system can do, and the spontaneity of the system. Because the Gibbs free energy shows the maximum available work a system can...

eduardomorales5

As temperature reaches zero, the entropy of the system reaches a constant value that reflects the degeneracy of the ground state.

eduardomorales5

If an ice cube is dropped into a hot coffee cup at 300K, how would we be able to determine how much ice would be needed to drop the temperature to 250K?

eduardomorales5

If the reduction potentials are both negative, do we take the largest value as the cathode, and the smallest as the anode?

eduardomorales5

How would the graph of a second order reaction look like? What can you find with the second order equation ?

eduardomorales5

If the compounds in the redox reaction are in aqueous or gaseous form, they need a conductor to help with the movement of electrons from one cell to the other. Platinum Pt(s) is a common conductor that can be used.

eduardomorales5

What is the difference between a first and second order reaction? Does increasing the concentration of a reactant increase the rate of the reaction?

eduardomorales5

If we decreased the concentration of a reactant, what would happen to the cell potential of the cell? If we decreased the mass of a reactant, what would happen to the cell potential?

eduardomorales5

What does it mean if the standard cell potential is negative? Will it be an oxidation reaction?

eduardomorales5

When would we use the change in U = q +w, and when would we use the change in U= H-PVdv? Does it matter which equation you use when calculating the change in internal energy?

eduardomorales5

Do electrolytes flow to the anode or cathode end? What is the purpose of the electrolytes in the redox reaction?

eduardomorales5

When drawing the cell diagrams, do we include water or represent it as H+ ions?

eduardomorales5

Conceptually, why does a negative cell potential produce a positive (non-spontaneous) Gibbs free energy?

eduardomorales5

How can we determine if the equilibrium constant of a reaction is greater than or less than 1 based on the Nernst equation?

eduardomorales5

Whats the difference between a concentration cell and a galvanic cell? Does one of them do more work than the other cell?

eduardomorales5

What does it tell us if the Gibbs free energy of the products is greater than the Gibbs free energy of the reactants?

eduardomorales5

If the Gibbs free energy value is positive, does it also imply that the reaction is endothermic? Or could the reaction also be exothermic?

eduardomorales5

Why do we have to include the OH- or H+ if a reaction is placed in an acidic or basic solution when balancing a redox reaction?

eduardomorales5

How does the standard electrode potential differ from the electrode potential?

eduardomorales5

How do you know what charge a compound has? Is it usually given or do you simply have to memorize the charges of molecules?

eduardomorales5

Why does decreasing pressure cause the reaction to shift toward the side that has more moles?

eduardomorales5

Why does adding more solid to a reaction not cause the equilibrium to shift? If I added more of a reactant, shouldn't the products increase as well regardless if it is solid?

eduardomorales5

Why does increasing the temperature cause an increase in the entropy of the system?

eduardomorales5

How do we determine if a reaction is spontaneous? What does having a Gibbs free energy of 0 mean relative to the energy of the reaction?

eduardomorales5

What is the difference between a state function and a path function? Are entropy, enthalpy and Gibbs free energy all examples of state functions?

eduardomorales5

How would you solve this problem? Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800.0 mL of 0.500 m HCl(aq). If the initial temperature of the hydrochloric acid solution is...

eduardomorales5

Why is the entropy of the universe always positive? And why does a larger temperature mean it has a smaller change in entropy?

eduardomorales5

When is the change in internal energy equal to 0? When is it equal to q? And what does it mean when the system is isothermal and irreversible?

eduardomorales5

What exactly is residual entropy and how would we calculate it if we were given a 50 molecules of NH3?

eduardomorales5

Negative entropy means there is a decrease in the disorder of the system or increase in the order of the system.

eduardomorales5

Yes, when the reaction is isothermal and reversible, you use that equation to calculate the change in entropy of the system.

eduardomorales5

What would be the net moles of the reaction if the reaction is OF2 + H20--> O2 + 2HF. How would I solve the problem given that I have 1 mole of OF2 and the change in enthalpy is equal to -318kJ?

eduardomorales5

For reversible work, the pressure gradually decreases as the volume of the system expands. At the start, the pressure outside the system matches the pressure inside of the system, so through infinitesimal changes in pressure, the volume of the gas will expand, and keep an equilibrium state with its ...

eduardomorales5

What exactly are microstates and how do they help determine the disorderness(entropy) of a system?

eduardomorales5

If the enthalpy of a reaction is 300kJ/mol, and we have 0.05mol of th substance, do we multiply or divide by the moles of the substance to find the enthalpy of the reaction?

eduardomorales5

If we are given grams of a substance, is it better to convert it to moles and use the molar heat capacity, or should I keep it in grams?

eduardomorales5

How can we use the standard enthalpy of formation to calculate the enthalpy of a reaction given a certain amount of moles. For instance, if we find the enthalpy of the reaction, how do you find the enthalpy at a specific mole value (i.e. 0.4 mol of a reactant)?

eduardomorales5

If we are given the heat capacity of the calorimeter, do we use that heat capacity to calculate the heat released by a chemical reaction? Or do we use the heat capacity of the molecules in the calorimeter?

eduardomorales5

Is enthalpy at constant pressure mean that the system has to be at 1.0atm and 25 degrees celsius? Or is it simply that it should be at 25 degrees celsius?

eduardomorales5

Make sure you use the correct gas constant. You probably used the 0.82 atm.L/mol.K, which got you the value that you have. Use 8.3145 J/mol.K and you should get the answer from the manual.

eduardomorales5

Why does temperature affect the K? Does increasing heat for an exothermic reaction shift it to the reactants or products?

eduardomorales5

Why doesn't adding an inert gas to a reaction increase the pressure and thus move the direction of the reaction a certain way?

eduardomorales5

To calculate the equilibrium constant, you use the ratio of the equilibrium concentrations of the products over the reactants. At equilibrium, the concentrations of A,B, and C should not change. We see that at the end of the graph. A was the reactant, while B and C were the products. The equilibrium...

eduardomorales5

How do buffers differ from the usual way that we calculate the concentrations using the ICE table?

eduardomorales5

The pKa and pKb tells us how well a compound dissociates in a solution(how fully it releases hydrogen or hydroxide ions) and tells us the strength of the acid or base. The pH tells us the concentration of H30+ ions that a compound gives off when placed in a solution, while the pOH tells us the conce...

eduardomorales5

Which is a stronger acid, CH3CH2OH or CH3COOH, and why? Is it due to the extra electronegative atom(the oxygen) or because of its resonance?

eduardomorales5

By drawing VSEPR structure, it takes the shape of a tetrahedral for both of the carbons. It would look like two tetrahedral bonded together by the carbon. So H3C-CH2BeH. The H3C would be a tetrahedral and so would the CH2BeH.

eduardomorales5

You would draw out the lewis structure and then compare the electronegativity of each of the atoms attached to the central atom. If there is an uneven distribution of charge throughout the molecule, then you would call the molecule polar.

eduardomorales5

An ion-dipole interaction is stronger than a dipole-dipole interaction because an ion has a stronger charge than a polar molecule.

eduardomorales5

For molecules that are highly symmetrical, like the trigonal bipyramidal, octahedral, and tetrahedral, the individual dipoles will usually cancel out, as they are typically non-polar molecular structures. However, if some of the atoms attached to a trigonal bipyramidal molecule, for example, are not...

eduardomorales5

You could compare the sizes of the two atoms and the number of protons that each atom has. Larger atoms have more orbitals and thus a greater amount of shielding electrons. The effective nuclear charge would not be as great as it would be for smaller atoms, and will be less able to pull electrons to...

eduardomorales5

What exactly causes an atom to have more electronegativity than other atoms?

eduardomorales5

Does electronegativity have to do with a dipole moment? Are we supposed to know how to calculate a dipole moment on a test?

eduardomorales5

So how does Lavelle want us to write the electron configuration of transition metals? Like for instance Vanadium, does he want us to write it like [Ar]4s2 3d3 or [Ar]4s1 3d4?

eduardomorales5

The equation is Zeff= Z-S, where Z is the atomic number and S is the number of shielding electrons(non-valence electrons).

eduardomorales5

I believe the answer was 1.00 x 10^5m/s, not the answer you gave. The rest of you answer is correct, in that it is reasonable because the electron is moving slower than the speed of light.

eduardomorales5

Ionization energy is the energy required to remove an electron from the valence shell. By removing one electron, there are more protons than electrons now, and thus the electrons are more tightly bound to the nucleus. Thus, the second ionization energy will be higher than the first now that it has t...

eduardomorales5

An element is most stable when its orbitals are full or half-full. In the case of Manganese, it has 7 valence electrons as you can see from its electron configuration [Ar]4s2 3d5, by counting the 2 electrons from the s-orbital and the 5 from the d-orbital. Because it is at a half filled d-orbital, i...

eduardomorales5

The electron configurations of Thallium is [Xe]4f14 5d10 6s2 6p1. Because it is Tl^+3, Thallium has lost 3 electrons. You remove the electrons in the order of the highest energy level, which in this case, is n=6. When you take the 3 away, you are left with [Xe]4f14 5d10.

eduardomorales5

Hund's Rule tells us that because of the repulsion of electrons, they will first try to occupy different orbitals while having parallel spin, which has less energy than opposite spin electrons. Because there are 3 p orbitals, they will try to fill up each orbital first until they other electrons beg...

eduardomorales5

The more correct one to use is the h/4pi.

eduardomorales5

What exactly is the order that electrons fill up orbitals? With what atoms do we start using the d-orbital?

eduardomorales5

How do we know when to put the spin number? How does an electron's spin affect its behavior?

eduardomorales5

The wavelength of an electron is Wavelength=10^-12m

eduardomorales5

The three fundamental equations were developed in the 1920s.

eduardomorales5

Constructive interference is when the peaks and troughs of two waves match and thus increase the amplitude of the wave.

eduardomorales5

Yes Lavelle explained it within his video modules.

eduardomorales5

The mass of an electron is 9.109x10^-31. The mass of a proton and neutron is 1.67x10^-27.

eduardomorales5

Bond length is the distance between the nuclei of two bonded atoms.

eduardomorales5

Make sure you study repeatedly over a long period of time. Don't cram the night before or that will contribute to your anxieties. Sleep and eat well, and take deep breathes to calm yourself down. Before the test, it is best not to think about it at all to avoid starting up any unnecessary anxiety. W...

eduardomorales5

It is best to round by the end of the problem and keep the precision of numbers during the problem to reach a more accurate answer. If you round too early, you might get a slightly lower or higher answer than what is correct. I would keep it at 1.007 for the sake of accuracy.

eduardomorales5

It is the accepted base SI unit that helps to standardize measurements so that scientists can more easily compare their findings using the same unit measurement.

eduardomorales5

Any non-zero number is significant. A zero is significant if it precedes the decimal point (e.g. 0.2) or if after the decimal point, precedes a non-zero(e.g. 0.004). So it given 500400, it would have 4 sig figs because the two zeroes in the middle precedes a non-zero, which in this case is 4. The ze...

Search found 77 matches